The invention is directed to an inexpensive builder material for use in detergent compositions. More particularly, the invention provides a selected crystalline calcium carbonate material substantially having a rhombohedral crystalline structure with {1,0-1,1} crystallographic indices. This very inexpensive builder material is especially suitable for use in detergent compositions used in fabric laundering, bleaching, automatic or hand dishwashing, hard surface cleaning and in any other application which requires the use of a builder material to remove water hardness.
It is common practice for formulators of cleaning compositions to include, in addition to a cleaning active material, a builder to remove hardness cations (e.g. calcium cations and magnesium cations) from washing solution which would otherwise reduce the efficiency of the cleaning active material (e.g. surfactant) and render certain soils more difficult to remove. For example, laundry detergent compositions typically contain an anionic surfactant and a builder to reduce the effects of hardness cations in wash solutions. In this context, the builder sequesters or xe2x80x9cties upxe2x80x9d the hardness cations so as to prevent them from hindering the cleaning action of the anionic surfactant in the detergent composition.
As is well known, water-soluble phosphate materials have been used extensively as detergency builders. However for a variety of reasons, including eutrophication of surface waters allegedly caused by phosphates, there has been a desire to use other builder materials in many geographic areas. Other known builders include water-soluble builder salts, such as sodium carbonate, which can form precipitates with the hardness cations found in washing solutions. Unfortunately, the use of such builders alone does not reduce the level of hardness cations at a sufficiently rapid rate. For practical purposes, the acceptable level is not reached within the limited time required for the desired application, e.g. within 10 to 12 minutes for fabric laundering operations in North America and Japan.
Moreover, some of these water-soluble builder salts, while attractive from the point of view of cost, have several disadvantages, among which are the tendency of the precipitates formed in aqueous washing solutions (e.g. insoluble calcium carbonate) to become deposited on fabrics or other articles to be cleaned. One alleged solution to this problem has been to include a water-insoluble material which would act as a xe2x80x9cseed crystalxe2x80x9d for the precipitate (i.e. calcium carbonate). Of the many materials suggested for such use, very small particle size calcite has been the most popular.
However, the inclusion of calcite in detergent compositions has been problematic because of the sensitivity of the hardness cation/salt anion (e.g. calcium/carbonate) reaction product to poisoning by materials (e.g. polyacrylate or certain anionic surfactants) which may be present in the washing solution. Without being limited by theory, the poisoning problem prevents the reaction product from forming in that crystallization onto the seed crystal is inhibited. Consequently, calcite typically has to be produced in a very small particle size in order to have a larger surface area which is harder to poison. This, however, renders the very small calcite particle dusty and difficult to handle. Moreover, the required particle sizes are so small (at least having 15 m2/g or more of surface area) that manufacturing of such calcite particles is extremely expensive. For example, production of such small calcite particles may require a controlled xe2x80x9cgrowingxe2x80x9d process which is extremely expensive. Another problem associated with the use of calcite as a xe2x80x9cseed crystalxe2x80x9d for the poisons and precipitates in washing solutions is the difficulty experienced in adequately dispersing the calcite in the washing solution so that it does not deposit on fabrics or articles which have been subjected to cleaning operations. Such deposits or residues are extremely undesirable for most any cleaning operation, especially in fabric laundering and tableware cleaning situations.
The prior art is replete with suggestions for dealing with the handling and dispersability problems associated with calcite. One previously proposed means for handling calcite is to incorporate it into a slurry, but this involves high storage and transportation costs. Another proposed option involves granulating calcite with binding and dispersing agents to ensure adequate dispersment in the wash solution. However, this option also has been difficult to implement effectively in modern day detergent compositions because the calcite granules have poor mechanical strength which continue to make them difficult to handle and process. Additionally, effective binding and dispersing agents for the calcite have not been discovered to date. Specifically, most of the binding and dispersing agents proposed by the prior art are themselves poisons which reduce the xe2x80x9cseed activityxe2x80x9d of the calcite. Consequently, it would be desirable to have an improved inexpensive builder material which overcomes the aforementioned limitations and is easy to handle, readily dispersible in washing solutions and exhibits improved builder performance.
Several additional builder materials and combinations thereof have also been used extensively in various cleaning compositions for fabric laundering operations and dish or tableware cleaning operations. By way of example, certain clay minerals have been used to adsorb hardness cations, especially in fabric laundering operations. Further, the zeolites (or aluminosilicates) have been suggested for use in various cleaning situations. Various aluminosilicates have also been used as detergency builders. For example, water-insoluble aluminosilicate ion exchange materials have been widely used in detergent compositions throughout the industry. While such builder materials are quite effective and useful, they account for a significant portion of the cost in most any fully formulated detergent or cleaning composition. In addition, such builders have a limited calcium sequestration capacity, and thus, are not very effective in hard water. Therefore, it would be desirable to have a builder material which performs as well as or better than the aforementioned builders, and importantly, is also less expensive.
Accordingly, despite the aforementioned disclosures, there remains a need in the art for an inexpensive builder material for use in detergent compositions which exhibits superior performance and is less expensive to manufacture in that it does not require a very small particle size. There is also a need in the art for such a builder material which is easy to handle (i.e., is not xe2x80x9cdustyxe2x80x9d), easy to process and readily disperses in washing solutions.
The following references are directed to builders for various detergent compositions: Atkinson et al, U.S. Pat. No. 4,900,466 (Lever); Houghton, WO 93/22411 (Lever); Allan et al, EP 518 576 A2; (Lever); Zolotoochin, U.S. Pat. No. 5,219,541 (Tenneco Minerals Company); Gamer-Gray et al. U.S. Pat. No. 4,966,606 (Lever); Davies et al, U.S. Pat. No. 4,908,159 (Lever); Carter et al, U.S. Pat. No. 4,711,740 (Lever); Greene, U.S. Pat. No.4,473,485 (Lever); Davies et al, U.S. Pat. No. 4,407,722 (Lever); Jones et al, U.S. Pat. No. 4,352,678 (Lever); Clarke et al, U.S. Pat. No. 4,348,293 (Lever); Clarke et al, U.S. Pat. No. 4,196,093 (Lever); Benjamin et al, U.S. Pat. No. 4,171,291 (Procter and Gamble); Kowalchuk, U.S. Pat. No. 4,162,994 (Lever); Davies et al, U.S. Pat. No. 4,076,653 (Lever); Davies et al, U.S. Pat. No. 4,051,054 (Lever); Collier, U.S. Pat. No. 4,049,586 (Procter and Gamble); Benson et al, U.S. Pat. No. 4,040,988 (Procter and Gamble); Cherney, U.S. Pat. No. 4,035,257 (Procter and Gamble); Curtis, U.S. Pat. No. 4,022,702 (Lever); Child et al, U.S. Pat. No. 4,013,578 (Lever); Lamberti, U.S. Pat. No. 3,997,692 (Lever); Cherney, U.S. Pat. No. 3,992,314 (Procter and Gamble); Child, U.S. Pat. No.3,979,314 (Lever); Davies et al, U.S. Pat. No. 3,957,695 (Lever); Lamberti, U.S. Pat. No.3,954,649 (Lever); Sagel et al U.S. Pat. No. 3,932,316 (Procter and Gamble); Lobunez et al, U.S. Pat. No. 3,981,686 (Intermountain Research and Development Corp.); Mallow et al, U.S. Pat. No. 4,828,620 (Southwest Research Institute); Bjorklund et al, xe2x80x9cAdsorption of Anionic and Cationic Polymers on Porous and Non-porous Calcium Carbonate Surfaces,xe2x80x9d Applied Surface Science 75 pp. 197-203 (1994); Wierzbicki et al, xe2x80x9cAtomic Force Microscopy and Molecular Modeling of Protein and Peptide Binding to Calcite,xe2x80x9d Calcified Tissue International 54, pp. 133-141 (1994); Park et al, xe2x80x9cTribological Enhancement of CaCO3 Dissolution during Scanning Force Microscopy,xe2x80x9d Langmuir, pp. 4599-4603, 12 (1996); and Nancollas et al, xe2x80x9cThe Crystallization of Calcium Carbonate,xe2x80x9d Journal of Colloid and Interface Science, Vol. 37, No. 4, pp. 824-829 (December 1971).
The aforementioned needs in the art are met by the present invention which provides a detergent builder in the form of a calcium carbonate that is in an especially selected crystalline form. Specifically, the crystalline calcium carbonate has a substantially rhombohedral crystal structure with {1,0-1,1} crystallographic indices. The crystalline calcium carbonate can be calcite that has been specially modified to the rhombohedral crystal structure with {1,0,-1,1} indices. The crystalline calcium carbonate of the present invention is extremely inexpensive because it can be readily formed from inexpensive naturally occurring calcite and it performs well even when used at large median particle sizes.
In accordance with one aspect of the invention, a detergent composition is provided. The detergent composition comprises: (a) an effective amount of crystalline calcium carbonate, the crystalline calcium carbonate substantially having a rhombohedral crystalline structure with {1,0,-1,1} crystallographic indices; and (b) at least about 1% by weight of a detersive surfactant.
In a preferred aspect of the invention, a detergent composition having especially preferred features is provided. This detergent composition comprises: (a) from about 0. 1% to about 80% by weight of crystalline calcium carbonate, the crystalline calcium carbonate substantially having a rhombohedral crystalline structure with {1,0,-1,1} crystallographic indices and a surface area of from about 0.01 m2/g to about 4 m2/g; (b) at least about 1% by weight of a detersive surfactant; and (c) from about 1% to about 80% by weight of sodium carbonate, wherein the sodium carbonate and the crystalline calcium carbonate are in a weight ratio of about 1:5 to about 5:1. This detergent composition is substantially free of phosphates.
The invention also provides a method for laundering soiled fabrics comprising the steps of contacting the soiled fabrics with an aqueous solution containing an effective amount of a detergent composition as described herein. Also provided is a method for cleaning surfaces comprising the steps of contacting the surfaces with an aqueous solution containing an effective amount of a detergent composition as described herein. Any of the detergent compositions described herein may be in the form of a laundry bar. In yet another method aspect of the invention, a method of removing calcium hardness ions from an aqueous solution is provided. This method comprises the step of dispersing crystalline calcium carbonate substantially having a rhombohedral crystalline structure with {1,0,-1,1} crystallographic indices into the aqueous solution, the calcium hardness ions crystallizing on the crystalline calcium carbonate resulting in the removal of the calcium hardness ions from the aqueous solution.
Accordingly, it is an object of the invention to provide a detergent composition containing an inexpensive builder material which exhibits superior performance and is less expensive to manufacture in that it does not require a very small particle size. It is also an object of the invention to provide such a builder material which is easy to handle (i.e.. is not xe2x80x9cdustyxe2x80x9d), easy to process and readily disperses in washing solutions. These and other objects, features and attendant advantages of the present invention will become apparent to those skilled in the art from a reading of the following detailed description of the preferred embodiment and the appended claims.
All percentages, ratios and proportions used herein are by weight (anhydrous basis) unless otherwise specified. All documents including patents and publications cited herein are incorporated herein by reference.